Plasma and Fusion Research: Regular Articles Volume 11, 2405112 (2016)

Nitrogen Hot Trap Design and Manufactures for Lithium TestLoop in IFMIF/EVEDA Project∗)

Eiichi WAKAI1), Kazuyoshi WATANABE1), Yuzuru ITO1), Akihiro SUZUKI2), Takayuki TERAI2),Juro YAGI3), Hiroo KONDO1), Takuji KANEMURA1), Tomohiro FURUKAWA1),

Yasushi HIRAKAWA1), Friedrich GROESCHEL4), Hiroshi TANAKA1),Koichi NAKANIWA1), Kouji FUJISHIRO1,4) and Haruyuki KIMURA1)

1)Japan Atomic Energy Agency, Ibaraki 319-1195, Japan2)University of Tokyo, Tokyo 113-8654, Japan

3)National Institute for Fusion Science, Gifu 509-5292, Japan4)IFMIF/EVEDA Project Team, Aomori 039-3212, Japan

(Received 1 December 2015 / Accepted 18 August 2016)

The lithium target facility of IFMIF (International Fusion Materials Irradiation Facility) consists of targetassembly, lithium main loop, lithium purification loops, the diagnostic systems, and remote handling system.Major impurities in the lithium loop are proton, deuterium, tritium, 7-Be, activated corrosion products and theother species (C, N, O). It is very important to remove nitrogen content in lithium loop during operation, in orderto avoid the corrosion/erosion of the nozzle of lithium target for the stable lithium flow on the target assembly.Nitrogen in the lithium can be removed by N hot trap using Fe-5%Ti alloy at temperatures from 400 to 600◦C. Inthis study, the specification and the detailed design were evaluated, and the component of N hot trap system wasfabricated.c© 2016 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords: IFMIF, IFMIF/EVEDA project, Li purification, nitrogen hot trap, Fe-Ti alloy

DOI: 10.1585/pfr.11.2405112

1. IntroductionIn parallel to the International Thermonuclear Exper-

imental Reactor (ITER) program, the Broader Approach(BA) activities [1, 2] are being implemented by the Eu-ropean Union (EU) and Japan (JA), aiming at the earlyrealization of the fusion energy. The BA activities com-prise the International Fusion Materials Irradiation Facil-ity/Engineering Validation and Engineering Design Activ-ities (IFMIF/EVEDA) [3, 4], the International Fusion En-ergy Research Center (IFERC) [5], and the Satellite Toka-mak [6] started from 2007 in the joint program. The mainfunction of the IFMIF is to generate the intense fusion neu-trons by injecting the deuteron beams accelerated to highenergy onto the liquid lithium flow at 250◦C. Guiding thelithium flow with a speed of 15 m/s along the concave backplate is required to increase the pressure in the lithiumflow by centrifugal force, to avoid boiling by the heat inputabout 1 GW of the deuteron beams [7] and to remove heatby the lithium flow circulation under the lithium purifica-tion controls by N hot trap, H hot trap, and cold trap [8–10].

According to the IFMIF design requirement, hydro-gen isotope content in the liquid lithium in the target fa-cility of the IFMIF is required to be less than 10 wppm,and tritium content in the liquid lithium is especially re-

author’s e-mail: wakai.eiichi@jaea.go.jp∗) This article is based on the presentation at the 25th International TokiConference (ITC25).

quired to be less than 1 wppm. Each of the other element(C, N, and O) contents in the liquid lithium is required to beless than 10 wppm. The solubility of both oxygen and car-bon in lithium is so low, less than 10 wppm around 200◦C,and their concentration in lithium can be controlled by acold trap. On the other hand, the solubility of nitrogenand hydrogen in lithium is large even at around the melt-ing point of lithium; therefore, both elements should be re-moved from the liquid lithium chemically with other traps,which are so called hot traps. The related recent activitiesof lithium purification studies were reported in the refer-ences [8–18], and the content of the lithium test facility ofIFMIF have been reported in the references [8, 9, 19–27].

This paper presents a design and the evaluation of anitrogen hot trap for removing nitrogen in Li loop in theIFMIF/EVEDA project.

2. Specification, Design and Manufac-ture of N Hot Trap SystemIn Table 1, main specification of purification system

and the related ones in the EVEDA Li test loop is summa-rized. Considering the experimental conditions and outputin previous nitrogen trap experiments on hot trapping byFe–Ti alloy, the temperature of the lithium would be betterto be increased to the range from 400◦C to 600◦C. Ther-mal convection is not suitable as the driving force because

c© 2016 The Japan Society of PlasmaScience and Nuclear Fusion Research

2405112-1

Plasma and Fusion Research: Regular Articles Volume 11, 2405112 (2016)

Table 1 Main specification of purification system and the relatedones in EVEDA Li test loop (ELTL) .

Fig. 1 Schematic image of nitrogen hot trap, showing lithiumflow. Top view (a) and side view (b).

the temperature difference in the loop may seriously affectthe trapping behavior. The shape of the trapping materialinstalled in the loop shall be a pebble of Fe-5Ti alloy, ap-proximately 0.16 mm in diameter, which is adopted as Nhot trap in EVEDA Li test loop (ELTL). The designed N

Fig. 2 The getter material of Fe-5at%Ti alloy pebbles.

Table 2 Specification of getter material.

Fig. 3 Manufactured N trap with 7 sampling tube.

hot trap has a pebble bed column and seven Li samplingbars as given in Fig. 1.

The getter material of Fe-5at%Ti alloy pebbles in thenitrogen hot trap is shown in Fig. 2, and the average di-ameter of the pebble was 0.16 mm. The specification ofgetter material in the nitrogen hot trap is given in Table 2.The nitrogen hot trap was fabricated in a frame work ofthe validation test. The picture of the manufactured N hottrap is shown in Fig. 3, and the temperature of the nitrogenhot trap can be controlled from room temperature to about600◦C.

Nitrogen impurity in the lithium can be removed by Nhot trap using Fe-Ti alloy at temperatures ranges from 400

2405112-2

Plasma and Fusion Research: Regular Articles Volume 11, 2405112 (2016)

Fig. 5 Schematic diagram of nitrogen trap which is a case of connection with Li test loop.

Fig. 4 Conceptual layout and system operation conditions forthe nitrogen hot trap, heat exchanger, pipe heater, and themain Li loop system operated at 250◦C.

to 600◦C. An example of the operation condition of N hottrap system is shown in Fig. 4, and it is controlled by heatexchanger, pipe heater, and N hot trap. The design of thevessel and pipes of N hot trap is evaluated by the analy-sis of materials properties such as creep, creep-fatigue andcorrosion. The nitrogen content in lithium loop during op-eration should be controlled to avoid the corrosion of thenozzle of lithium target under less than about a hundredppm. Li inlet pipe conducted from main loop to N trapsystem is unique line.

The lithium passing rout from inlet pipe to outlet pipeis shown in the schematic diagram of nitrogen trap in acase of the Li test loop as given in Fig. 5.

3. SummaryThis paper evaluated a specification and the design of

a nitrogen hot trap for removing nitrogen impurity in Liin the IFMIF/EVEDA project. The nitrogen hot trap wasfabricated in a frame work of the validation test. Nitro-gen in the lithium can be removed by N hot trap using a

Fe-5at%Ti alloy at temperatures from 400 to 600◦C. Thedesign of the vessel and pipes of N hot trap was evaluatedby the analysis of materials properties such as creep, creep-fatigue and corrosion. The nitrogen content in lithium loopduring operation should be controlled to avoid the corro-sion/erosion of the nozzle of lithium target under less thanabout 10 - 30 wppm. The specification evaluation, the de-tailed design, and the component’s manufacturing of N hottrap system were carried in the EVEDA project.

AcknowledgmentsThis study was performed under the IFMIF/EVEDA

project. Authors are grateful to Drs. S. Ohira, M. Sugi-moto of JAEA, Dr. R. Heidinger of F4E, Drs. J. Knasterand H. Matsumoto of IFMIF/EVEDA project team, Profs.T. Muroga and T. Nishitani of NIFS for their supports andhelpful discussions.

[1] S. Matsuda, Fusion Eng. Des. 82, 435 (2007).[2] T. Nishitani et al., Fusion Eng. Des. 88, 422 (2013).[3] M. Araki et al., Fusion Eng. Des. 85, 2196 (2010).[4] P. Garin and M. Sugimoto, J. Nucl. Mater. 417, 1262

(2011).[5] J. Knaster et al., Nucl. Fusion 53, 116011 (2013).[6] T. Fujita et al., Nucl. Fusion 47, 1512 (2007).[7] M. Ida et al., Fusion Eng. Des. 70, 95 (2004).[8] E. Wakai et al., Fusion Sci. Technol. 66, 46 (2014).[9] E. Wakai et al., J. Plasma Fusion Res. 88, 691 (2012).

[10] H. Nakamura et al., Fusion Eng. Des. 83, 1007 (2008).[11] K. Natesan, J. Nucl. Mater. 115, 251 (1983).[12] J. Yagi et al., Fusion Eng. Des. 86, 2678 (2011).[13] T. Furukawa et al., Fusion Eng. Des. 89, 2902 (2014).[14] J. Yagi et al., J. Nucl. Mater. 417, 710 (2011).[15] S. Hirakane et al., Fusion Eng. Des. 75, 721 (2005).[16] S. Hirakane et al., Fusion Eng. Des. 81, 665 (2006).

2405112-3

Plasma and Fusion Research: Regular Articles Volume 11, 2405112 (2016)

[17] H. Kondo et al., Fusion Eng. Des. 86, 2437 (2011).[18] H. Kondo et al., Nucl. Fusion 51, 123008 (2011).[19] S. Hirakane et al., Fusion Eng. Des. 75, 721 (2005).[20] S. Hirakane et al., Fusion Eng. Des. 81, 665 (2006).[21] T. Furukawa et al., Fusion Eng. Des. 98-99, 2138 (2015).[22] T. Kanemura et al., Fusion Eng. Des. 89, 1642 (2014).

[23] J. Knaster et al., Fusion Eng. Des. 89, 1709 (2014).[24] K. Esaki et al., J. Plasma Fusion Res. SERIES 11, 36

(2015).[25] P. Favuzza et al., Fusion Eng. Des. 107, 13 (2016).[26] K. Hiyane et al., Fusion Eng. Des. 109-111, 1340 (2016).[27] E. Wakai et al., Nucl. Mater. Energy (2016), in press.

2405112-4